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#1462079 - 19/04/2018 08:49 Re: NSW April 7-15 2018, sustained April Heatwave leading to a possibly record month [Re: Surly Bond]
kizz Offline
Weatherzone Addict

Registered: 11/02/2002
Posts: 1990
Loc: Beacon Hill, Sydney 152m asl
Originally Posted By: Surly Bond
With data handling now so easy, I am surprised that climate normals are not published for each day of the year, rather than for each month.

As they do in the US with their records?

I have looked at that with all the Sydney sites and found that the daily normal plots are far from a nice and smooth sine curve through the year. Obviously the newer the site the more the daily means jump about. You need decades of data before you can stop applying any 'smoothing' methods to remove the ugly seismograph look.

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#1462101 - 19/04/2018 14:12 Re: NSW April 7-15 2018, sustained April Heatwave leading to a possibly record month [Re: DerekHV]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2113
Loc: Manilla, near Tamworth NSW
Hi kizz

I didn't know they published daily normals in the US. Using them makes much more sense.

You are right that average values for a given day of the year do not settle down well in any realistic length of record. Even repeated smoothing does not yield a simple seasonal pattern.
I established my normal curves by first repeatedly smoothing the data from my chosen 10-year normal period, then fitting harmonic curves by eye. I got an acceptable fit by using a fundamental and three harmonics.

I show the normal curves on each of my monthly and seasonal weather reports. The shape is easier to see on the seasonal reports:
https://climatebysurly.com/category/manilla-nsw/season-weather/
The main departure from a simple harmonic cycle at my site is to higher daily maximum temperature in September-October.

I wonder how the US daily normals were determined.
_________________________
Data are cheap; information is expensive!

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#1462185 - 20/04/2018 09:29 Re: NSW April 7-15 2018, sustained April Heatwave leading to a possibly record month [Re: DerekHV]
kizz Offline
Weatherzone Addict

Registered: 11/02/2002
Posts: 1990
Loc: Beacon Hill, Sydney 152m asl
I would never trust myself to fit "by eye". I just would not be able to do it! I would most definitely find a mechanical method.

When I said records in the US I meant the extremes for each date. It does make more sense for them especially in Spring and Autumn. I wouldn't know about the daily means.

I imagine that they would have daily means but I'm not sure what smoothing method, if any, is the official method at NOAA or even AccuWeather, Wunderground etc.
One of those things that I would search for if I had all the time in the world!

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#1462190 - 20/04/2018 10:18 Re: NSW April 7-15 2018, sustained April Heatwave leading to a possibly record month [Re: DerekHV]
Blair Trewin Offline
Weatherzone Addict

Registered: 13/07/2001
Posts: 3796
Loc: Melbourne, Australia
I know the NOAA normals have some form of smoothing but not sure exactly what. I did some work a while back which indicated that (for Australian data at least) a straightforward linear interpolation between monthly means worked as well as more complicated methods.

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#1462210 - 20/04/2018 11:58 Re: NSW April 7-15 2018, sustained April Heatwave leading to a possibly record month [Re: DerekHV]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2113
Loc: Manilla, near Tamworth NSW
Thanks, Blair. Such things are hard to find out.

To kizz. My fitting is not simply "by eye". I try a harmonic curve with particular constants, and overlay it on the graph of data. I also make a difference graph. Then I try other constants, and further orders of harmonics, to reduce the differences.
_________________________
Data are cheap; information is expensive!

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#1463453 - 09/05/2018 16:37 Re: NSW April 7-15 2018, sustained April Heatwave leading to a possibly record month [Re: DerekHV]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2113
Loc: Manilla, near Tamworth NSW

The return to normal temperatures in the final week of April made the averages for the month less anomalous than I had thought they would be.
The anomalies I had suggested (on 18 April at 14:10) were:
Max +4, Mean +4, Min +2.
Those finally recorded were:
Max +2.8, Mean +2.4, Min +2.1.
The Min and Mean were 21st century April records (by small margins) but the Max was not. The mean Max of April 2005 was 0.6 degrees higher than the mean Max this April.
https://climatebysurly.com/2018/05/08/april-2018-very-warm-and-sunny/
_________________________
Data are cheap; information is expensive!

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#1466215 - 21/06/2018 19:11 Re: NSW April 7-15 2018, sustained April Heatwave leading to a possibly record month [Re: DerekHV]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2113
Loc: Manilla, near Tamworth NSW
This graph puts the heat wave of early April 2018 in context, at least at one station near Tamworth.



The graph is in my blog at "Autumn 2018 dry and very warm"

So far, June temperatures are about normal, day and night.
_________________________
Data are cheap; information is expensive!

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